Categorization and icons

So, now that I have a reasonable understanding of how this beast works, I am ready to categorize all of my content.

As I have been doing with all of my characters, I am looking to load each of the assets I have and save them as presets, ensuring that all my assets have the .duf format. Then, I'll be able to delete all the .cr2, dba, etc...

Before I go too far, let me know if this is a bad idea. So far, it worked wonders for my characters, as I have them all in one place and have only to double-click them to have them in my scene.

One question though: what does make the categorization appear on the assets icons.